The Allen-Bradley 1746-NR8 is a high-density RTD/Resistance Analog Input Module for the SLC 500 control platform. This module offers eight isolated input channels, making it an excellent choice for applications requiring multiple temperature or resistance measurements from a single chassis slot. It supports a broad range of RTD sensors, including Platinum (385 & 3916), Copper (426), Nickel (618 & 672), and Nickel Iron (518). Furthermore, the 1746-NR8 accepts direct resistance inputs across four selectable ranges. Its sigma-delta A/D conversion and programmable digital filtering deliver stable, accurate readings even in challenging industrial environments. For added convenience, the module performs automatic self-calibration at power-up or on a programmed cycle.
The 1746-NR8 offers impressive technical capabilities. It provides a resolution of 0.01°C, which ensures precise temperature tracking across its measurement range. The module's update time is configurable from 6 milliseconds to 2 seconds, allowing you to optimize between speed and filtering for your specific process. Additionally, it uses a sigma-delta modulation method for analog-to-digital conversion, which effectively rejects high-frequency noise. The step response is rated at 60 ms in and 2.5 ms out, which means the module reacts quickly to input signal changes. For input filtering, the 1746-NR8 incorporates a programmable low-pass digital filter that you can adjust to match the noise characteristics of your installation. Consequently, this module maintains high signal integrity even when installed near variable-frequency drives or other noise-generating equipment.
This module supports an extensive list of RTD types, providing great flexibility for various temperature sensing needs. Specifically, it works with Platinum RTDs having Alpha values of 385 (100, 200, 500, 1000 Ω) and 3916 (100, 200, 500, 1000 Ω). It also supports Copper (426) 10 Ω, Nickel (618) 120 Ω, Nickel (672) 120 Ω, and Nickel Iron (518) 604 Ω. Beyond temperature measurement, the 1746-NR8 accepts direct resistance inputs across four ranges: 0-150Ω, 0-500Ω, 0-1000Ω, and 0-3000Ω. Therefore, you can use this module to measure position, displacement, or level by connecting potentiometers or slide-wire devices. Each channel includes broken sensor detection that immediately flags open or shorted circuits by outputting an out-of-range value. This feature simplifies troubleshooting and minimizes system downtime.
The Allen-Bradley 1746-NR8 supports 2-wire, 3-wire, and 4-wire RTD connections, giving you flexibility based on your accuracy requirements and cable length. For a 2-wire RTD, Belden 9501 shielded cable or an equivalent works well. However, keep cable runs short for 2-wire setups because lead resistance can introduce measurement errors. If long runs are unavoidable, use a lower gauge cable like AWG #16 instead of AWG #24 to minimize resistance. For 3-wire or 4-wire RTDs, Belden 9533 or Belden 83503 cables are suitable choices. These configurations compensate for lead wire resistance, delivering greater accuracy over longer distances. Importantly, the removable terminal block (RTB) terminals accept single-wire connections only. Also, you must use shielded cables and ground the shield at one end to prevent ground loops and ensure stable readings. The terminal block compatible with this module is the Allen-Bradley 1746-RT-35.
The 1746-NR8 is engineered for reliable operation in demanding industrial settings. It operates within an ambient temperature range of 0°C to 60°C and can withstand storage between -40°C and 85°C. The module also tolerates a non-condensing relative humidity of 5% to 95%. For electrical isolation, it provides 500 Volts AC for one minute between the inputs and the backplane, as well as between the inputs and the chassis ground. Continuous isolation of 5 Volts DC exists between channels. The maximum common-mode voltage is ±1 Volt. Furthermore, the 1746-NR8 draws 100 mA from the 5V DC backplane supply and 55 mA from the 24V DC supply. Its total backplane power consumption reaches a maximum of 1.82 W (0.5 W at 5V DC and 1.32 W at 24V DC). This efficient power design reduces thermal buildup inside the chassis. The module's front panel features LED status indicators for the module health and for each of the eight channels, enabling quick visual diagnostics.
Installing the Allen-Bradley 1746-NR8 is simple and straightforward. You can place it in any slot of an SLC 500 chassis, except for Slot 0, which is reserved for the processor or an adapter module. This module is compatible with both fixed and modular SLC 500 hardware styles. In a fixed system, it typically installs in a 1746-A2 expansion chassis. Meanwhile, in a modular system, it fits into any local or remote I/O chassis. The module occupies a single slot and draws its power directly from the backplane, so no external power supply is required. Auto-calibration occurs at power-up and can also run every 5 minutes, ensuring consistent measurement accuracy over time without manual intervention. During installation, match the sensor wiring to the correct channel terminals and configure the input type and filter settings in your SLC 500 program for optimal performance.
1 x Allen-Bradley 1746-NR8 RTD/Resistance Input Module
1 x Installation Instructions Manual
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1. Can I install the 1746-NR8 in any slot of my SLC 500 chassis?
No. The 1746-NR8 can occupy any slot except Slot 0. Slot 0 is exclusively reserved for the SLC 500 processor or a communication adapter module.
2. What RTD sensors are compatible with the 1746-NR8?
This module supports Platinum (385 & 3916) in 100, 200, 500, and 1000 Ω; Copper (426) 10 Ω; Nickel (618 & 672) 120 Ω; and Nickel Iron (518) 604 Ω. It also accepts direct resistance inputs.
3. What is the advantage of using a 3-wire or 4-wire RTD with this module?
A 3-wire or 4-wire configuration compensates for lead wire resistance. This compensation delivers more accurate measurements, especially over long cable runs, compared to a 2-wire setup.
4. How does the 1746-NR8 indicate a broken sensor condition?
The 1746-NR8 includes built-in broken sensor detection. If a channel detects an open or shorted circuit, it outputs an out-of-range value. Your control program can then identify this as a fault condition.
5. Does the 1746-NR8 require an external power supply?
No. The 1746-NR8 draws its operating power directly from the SLC 500 backplane. It consumes 100 mA at 5V DC and 55 mA at 24V DC, with a total power consumption of 1.82 W maximum.
| Brand Name | |
| Model No. | 1746-NR8 |
| Product Type | Analog Input Module |
| hasMerchantReturnPolicy | Adjust according to reality |
| Shippingdetails | Adjust according to reality |
